This invention relates generally to detection circuits and more particularly to an edge sensitive detection circuit.
Detection circuits are widely used in electronic equipment to detect an event that triggers initiation of a corresponding response. For example, detection circuits are widely used in computers, automobile engine control systems, microwave ovens, coffee makers, etc. In computers, an event may be power on, power down, standby, reset, an interrupt, change in settings, etc., where each of the events has a corresponding response. For example, the power on event has a corresponding response that turns the computer on in a predetermined manner.
As is known, a computer includes multiple layers of software and/or hardware that include detection circuitry/software and/or response circuitry/software. To process a corresponding response from a detected event, different elements of the software and/or hardware process different aspects of the corresponding response and detecting the event. For example, for a power on sequence, a detection circuit must first detect the power on condition. For the xe2x80x9cpower onxe2x80x9d detection circuit to detect a power on event, it must be receiving power. As such, the xe2x80x9cpower onxe2x80x9d detection circuit is either operably coupled to a battery source or is included in the power supply. Before any of the associated software can be processed, the central processing unit (CPU) must be receiving power, the clocks must be up and running, and the interoperability between the CPU and memory must be up and running.
With power applied to the hardware components of the computer, the power on software may now be processed. Such power on software includes system BIOS, enabling the operating system, enabling video graphics processing, and enabling other peripheral components. Because of the distributed nature of the computer system, events are typically triggers as a logic setting. For example, a reset condition may occur when a reset pin is pulled to a logic xe2x80x9c0xe2x80x9d state and the reset condition is removed when the reset pin is pulled to a logic xe2x80x9c1xe2x80x9d state. Thus, an event is triggered when the detection circuit detects a predetermined logic state on a corresponding pin and no event occurs, or the event is removed, when the detection circuit detects an alternate predetermined logic state.
While logic state triggering of events works well in distributed systems, such as a computer, it does not work well in integrated systems. An integrated system has a difficult time processing events, such as power down, reset, standby, set, and power up when the event is triggered via a logic state change. The difficulty arises because the software that overwrites the logic state of the event needs to be active, such that the detection circuit may detect a change in the logic state of the event. However, the processor and memory interfaces cannot be activated to process the software to change the logic state of the event until the detection circuit detects a change in the logic state. Thus, a chicken and egg dilemma arises.
Therefore, a need exists for a detection circuit that overcomes the above described problems.